HaRP, or Haskell Regular Patterns, is a Haskell extension that extends
the normal pattern matching facility, allowing the user to match against
regular expressions. This expressive power is highly useful in a wide
range of areas, including text parsing and XML processing. Regular
expression patterns in HaRP work over ordinary Haskell lists ([]) of
arbitrary type. HaRP is implemented as a pre-processor to ordinary Haskell.